In want to use a customized list box in my application. i hav used the sample code from this link

In the sample the Custom list class is extended from CEikTextListBox. This sample works for me.
But i would like to know whether can i directly extend the class from CEikListBox which is the base class. i have gone thru some forums where they hav mentioned this can't be done.
Please Explain.

Thanks & Regards,
R Jyothi Lakshmi